Starting at the bottom, wrap the yarn around one of the pins then bring it to the next pin, wrap it around and repeat. Keep weaving the yarn back and forth around the pins until you have one big web. If necessary, use the glue gun on the yarn to keep it from moving.
Wrap the yarn around the pins until all the pumpkins are covered. CAUTION: The pins will be sticking out inside of the pumpkin, so be careful how you hold it.
Tie or glue small strands of yarn to several of the spiders. Tie the strands to the webbing so the spiders will hang down. Then glue some spiders directly to the webbing. Add several to the top to make it look like they are escaping. Place a few on the floor and make them look like they are about to scatter.
Insert a flashlight into the top pumpkin to illuminate the large spider. Then place the spider as if she's escaping, too (again, be careful of the pins).